This invention is related to a semiconductor article and a method for processing of semiconductor devices. In particular, the invention is directed to an improved method of treatment of a semiconductor device undergoing processing after a via has been etched in the insulating dielectric layer. Further, the invention is particularly directed to applying an OH/H containing plasma for removal of metal containing residues from a dielectric layer of a via of a semiconductor device.
When a semiconductor device is manufactured, a necessary step in the processing is to create vias in the dielectric layers of the device. A via is an opening in the layer structure that is typically etched through various dielectric layers in the device. These layers have been deposited to form an insulating layer between two adjacent metallic layers. Etching vias and filling them with tungsten, or other appropriate materials, enable an electrical connection to be made between particular metal lines of the device being manufactured. Vias are conventionally etched by a fluorine-based plasma (such as tetrafluoromethane or hexafluoroethane) and are cleaned by a combination of an oxygen plasma and a solvent to remove residual organic materials and leave a clean electrically-conducting surface at the bottom of via. This cleaning process, while effective in removing organic residues such as photoresist and hydrocarbon polymers, cannot remove organometallic residues containing titanium or aluminum. Such residues are formed at the bottom of vias as titanium, titanium nitride, and/or aluminum are sputtered from the metal line underneath vias during the etch. It is preferable to have a via that is free of these residues in order to provide low and uniform resistivity for the large number of vias typically needed for an end product semiconductor device.
FIG. 1 is a cross-section of a typical via 20 produced by a process used in the prior art, such as etching with a plasma of C2F6/C4F8/CF4. The via 20 has been etched through an insulating layer 22 of a semiconductor device 23 that is being processed. The layer 22 is typically an interlayer dielectric, such as tetraethylorthosilicate (TEOS), which is disposed on a TiN layer 24 and an Al layer 26. In order to clean the via 20, the process applies an oxygen plasma 21 to the via 20 and then completes the cleaning of the via 20 by applying a solvent to the via 20. This prior art process thus involves (a) forming the via 20 in the layer 22 by the etch process described above, (b) applying the oxygen plasma 21 to remove photoresist which has remained and also remaining organic residues from the via etch step, (c) applying a solvent to remove some of the residues and (d) performing another step using the oxygen plasma 21 for a final cleaning step. The disadvantage of this process used in the prior art is the presence of the residual organometallic deposit 28 that has not been removed by this process. The organometallic deposit 28 can, for example, be one or more of titanium and/or aluminum compounds with carbon and nitrogen.
According to one form of the present invention, after a via is etched in a semiconductor device or dielectric layer that is being processed, the via is cleaned by the application of a water-vapor plasma, followed by applying a plasma that is a mixture of oxygen and tetrafluoromethane. In another embodiment, the water vapor and oxygen tetrafluoromethane plasma etch cleaning can be carried out in a combination single step. The results leave a clean via in the layer structure without leaving residual amounts of organic compounds which contain metals, such as, titanium or aluminum. The OH/H containing plasma in either embodiment also cleans residues from the inside of the chamber in which the via is etched. In a generic form of the invention, the cleaning process involves the formation of a plasma containing OH/H species from any source, and the OH/H species are believed to be most important for cleaning vias. This step is then followed by use of oxygen and a fluorine-based constituent.
Additional advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein only preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of being practiced in a number of different embodiments, and its details are capable of modifications in various ways, all without departing from the scope of the invention. Accordingly, the drawings, description and examples are to be regarded as illustrative in nature and not as restrictive.